This invention relates generally to prosthetic heart valves for replacement of diseased or damaged natural heart valves, and relates particularly to prosthetic heart valves which use flexible leaflets of synthetic material which mutually coapt to permit flow in only one direction, somewhat like natural valves. Such valves can provide good flow performance with little disturbing noise or vibration, but were initially considered not to have sufficient durability. This deficiency now seems to have been remedied by development of better synthetic materials and methods of assembly, together with designs which permit suitably low cyclic strain on the flexible material.
With the foregoing problems in hand, a further problem has appeared: chronic thrombus formation and actual tissue overgrowth, particularly around the upstream end of the prosthetic valve, occurs far too often.